1. Field of the Invention
This invention relates to a surgical stapling instrument for joining hollow body organs and more particularly to a vented anvil assembly having channels for facilitating flow of gas, tissue and other debris between outer and inner surfaces of the anvil assembly during use.
2. Description of the Prior Art
Heretofore, it has been known to use surgical staplers to connect hollow body organs. Typically, the stapling device consists of a handle portion, an elongated portion, a staple carrying portion, and an anvil carrying portion. In use, the anvil carrying portion is positioned in one hollow body organ and the stapling carrying portion of the instrument is positioned in a second hollow body organ. The anvil carrying portion is then attached to the staple carrying portion and retracted towards the staple carrying portion, thereby drawing the two hollow body organs together into an abutting relationship. As the tissue sections are drawn together, air, tissue and other debris are usually trapped and compressed in the confined space between the staple carrying portion and the anvil carrying portion. This can result in undesirable pressure build up in the space between the anvil and staple carrier, which can interfere with the anastomosis.
When the tissue is sufficiently drawn or clamped together, the instrument is fired to eject the staples from the staple carrying portion. The staples pass through the clamped tissue sections and are formed against the anvil carrying portion thereby securing the tissue sections together. Subsequently, a circular knife member is advanced through excess tissue and into a knife abutment ring on the anvil. Movement of the knife within the confined space between the staple carrying portion and the anvil carrying portion further reduces the volume of space in which excess tissue fluid and other debris are trapped. Because tissue and fluids are relatively incompressible, this additional reduction in volume can also create high pressures and tissue trauma in the confined space.
To relieve this undesirable increase in pressure in the confined space, several instruments have been provided with venting means, in the form of vent holes, in the anvil and staple carrying portions leading outward from the enclosed space. Examples of such venting means can be found in commonly assigned U.S. Pat. Nos. 4,606,343; 4,603,693; and 4,573,468 to Conta et al.; and 4,351,466 to Noiles. It has been observed that without the vent holes there is a tendency for the tissue to extrude outward between the clamped faces of the staple carrying portion and the anvil carrying portion. In instruments having vent holes in the anvil portion, it is common to find tissue in significant quantity extruded into and through these vent holes. In some instances, the excess tissue and other debris extruded through the vent holes may plug the vent holes due to the proximity of the adjacent hollow organ tissue section.
While the aforementioned devices generously vent the interior of the stapling mechanism to prevent the buildup of excess pressure in the confined space within the stapling mechanism, if the vent holes are blocked by tissue and other debris, a suction effect between the adjacent hollow body tissue section and the anvil can occur when the instrument is withdrawn from the body. This suction effect is undesirable during removal of the stapler. Thus, there exists a need to reduce the suction effect between an outer surface of the anvil portion and the surrounding tissue sections during removal of the anvil from the tissue section and to reduce blockage of the vent holes by extruded tissue and other debris.